ISAJET 7.84 A Monte Carlo Event Generator Reactions

ISAJET 7.84 A Monte Carlo Event Generator

for pp, p?p, and e+e- Reactions

Frank E. Paige and Serban D. Protopopescu Physics Department

Brookhaven National Laboratory Upton, NY 11973, USA

Howard Baer Department of Physics and Astronomy

University of Oklahoma Norman, OK 73019

Xerxes Tata Department of Physics and Astronomy

University of Hawaii Honolulu, HI 96822

Contents

1 Introduction

4

2 Physics

5

2.1 Hard Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.1 Minbias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.2 Twojet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.3 Drellyan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1.4 Photon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.5 Wpair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.6 Higgs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.1.7 WHiggs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1.8 SUSY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1.9 SUSY Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.10 e+e- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.1.11 Technicolor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.1.12 Extra Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2 Multiparton Hard Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.2.1 Z + 2 jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.3 QCD Radiative Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.4 Jet Fragmentation: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.5 Beam Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1

3 Sample Jobs

21

3.1 DEC VMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.2 IBM VM/CMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.3 Unix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4 Patchy and PAM Organization

28

5 Main Program

34

5.1 Interactive Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.2 User Control of Event Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.3 Multiple Event Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.4 Main Programs for ISASUSY and ISASUGRA . . . . . . . . . . . . . . . . . 39

6 Input

41

6.1 Input Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

6.2 Optional Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6.3 Kinematic and Parton-type Parameters . . . . . . . . . . . . . . . . . . . . . 52

6.4 SUSY Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6.5 Forced Decay Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6.6 Parton Distributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

6.7 Multiparton Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7 Output

58

7.1 Beginning Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

7.2 Event Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.3 End Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.4 LesHouches Event output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

8 File Reading

67

9 Decay Table

68

10 IDENT Codes

69

11 Higher Order Processes

79

12 ISASUSY: Decay Modes in the Minimal Supersymmetric Model

82

13 IsaTools

90

13.1 IsaRED (H. Baer, C. Balazs and A. Belyaev) . . . . . . . . . . . . . . . . . . 90

13.2 IsaBSG (H. Baer and M. Brhlik) . . . . . . . . . . . . . . . . . . . . . . . . 90

13.3 IsaAMU (H. Baer and C. Balazs) . . . . . . . . . . . . . . . . . . . . . . . . 91

13.4 IsaBMM (J. K. Mizukoshi, X. Tata and Y. Wang) . . . . . . . . . . . . . . . 91

13.5 IsaRES (C. Balazs, A. Belyaevand M. Brhlik) . . . . . . . . . . . . . . . . . 92

13.6 Compiling and Using IsaTools (F. Paige) . . . . . . . . . . . . . . . . . . . . 93

2

14 Deriving the Weak Scale Couplings from the RGEs: RGEFLAV

95

14.1 The Input File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

14.2 Entering a General Unitary Matrix . . . . . . . . . . . . . . . . . . . . . . . 98

14.3 Weak Scale Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . 99

14.4 Boundary Conditions at the High Scale . . . . . . . . . . . . . . . . . . . . . 100

14.5 Electroweak Symmetry Breaking . . . . . . . . . . . . . . . . . . . . . . . . . 101

14.6 Iterative Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

14.7 RGEFLAV Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

14.8 The Decay Subroutine, SQSIX . . . . . . . . . . . . . . . . . . . . . . . . . . 106

15 Changes in Recent Versions

108

15.1 Version 7.84, June 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

15.2 Version 7.83, June 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

15.3 Version 7.82, June 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

15.4 Version 7.81, April 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

15.5 Version 7.80, October 2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

15.6 Version 7.79, December 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

15.7 Version 7.78, March 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

15.8 Version 7.75, January 2007 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

15.9 Version 7.74, February 2006 . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

15.10Version 7.72, August 2005 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

15.11Version 7.70, October 2004 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

15.12Version 7.69, August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

15.13Version 7.64, September 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . 113

15.14Version 7.63, April 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

15.15Version 7.58, August 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

15.16Version 7.51, May 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

15.17Version 7.47, December 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

15.18Version 7.44, April 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

15.19Version 7.42, January 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

15.20Version 7.40, October 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

15.21Version 7.37, April 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

15.22Version 7.32, November 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

15.23Version 7.31, August 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

15.24Version 7.30, July 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

15.25Version 7.29, May 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

15.26Version 7.27, January 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

15.27Version 7.22, July 1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

15.28Version 7.20, June 1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

15.29Version 7.16, October 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

15.30Version 7.13, September 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . 120

15.31Version 7.11, September 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . 120

15.32Version 7.10, July 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

3

1 Introduction

ISAJET is a Monte Carlo program which simulates pp, p?p and e+e- interactions at high energies. ISAJET is based on perturbative QCD plus phenomenological models for parton and beam jet fragmentation. Events are generated in four distinct steps:

? A primary hard scattering is generated according to the appropriate QCD cross section. ? QCD radiative corrections are added for both the initial and the final state. ? Partons are fragmented into hadrons independently, and particles with lifetimes less

than about 10-12 seconds are decayed. ? Beam jets are added assuming that these are identical to a minimum bias event at the

remaining energy. ISAJET incorporates ISASUSY, which evaluates branching ratios for the minimal supersymmetric extension of the standard model. H. Baer and X. Tata are coauthors of this package, and they have done the original calculations with various collaborators. See the ISASUSY documentation in the patch Section 12. ISAJET is supported for ANSI Fortran and for Cray, DEC Ultrix, DEC VMS, HP/9000 7xx, IBM VM/CMS 370 and 30xx, IBM AIX RS/6000, Linux, Silicon Graphics 4D, and Sun computers. The CDC 7600 and ETA 10 versions are obsolete and are no longer supported. It is written mainly in ANSI standard FORTRAN 77, but it does contain some extensions except in the ANSI version. The code is maintained with a combination of RCS, the Revision Control System, and the Patchy code management system, which is part of the CERN Library. The original sources are kept on physgi01.phy. in ~isajet/isalibrary/RCS; decks revised in release n.nn are kept in ~isajet/isalibrary/nnn. ISAJET is supplied to BNL, CERN, Fermilab, and SLAC; it is also available from



or by request from the authors. Patch ISAPLT contains the skeleton of an HBOOK histogramming job, a trivial calorime-

ter simulation, and a jet-finding algorithm. (The default is HBOOK4; HBOOK3 can be selected with a Patchy switch.) These are provided for convenience only and are not supported.

4

2 Physics

ISAJET is a Monte Carlo program which simulates pp, p?p and e+e- interactions at high energy. The program incorporates perturbative QCD cross sections, initial state and final state QCD radiative corrections in the leading log approximation, independent fragmentation of quarks and gluons into hadrons, and a phenomenological model tuned to minimum bias and hard scattering data for the beam jets.

2.1 Hard Scattering

The first step in simulating an event is to generate a primary hard scattering according to some QCD cross section. This has the general form

= 0F (x1, Q2)F (x2, Q2)

where 0 is a cross section calculated in QCD perturbation theory, F (x, Q2) is a structure function incorporating QCD scaling violations, x1 and x2 are the usual parton model momentum fractions, and Q2 is an appropriate momentum transfer scale.

For each of the processes included in ISAJET, the basic cross section 0 is a two-body one, and the user can set limits on the kinematic variables and type for each of the two primary jets. For DRELLYAN and WPAIR events the full matrix element for the decay of the W's into leptons or quarks is also included.

The following processes are available:

2.1.1 Minbias

No hard scattering at all, so that the event consists only of beam jets. Note that at high energy the jet cross sections become large. To represent the total cross section it is better to use a sample of TWOJET events with the lower limit on pt chosen to give a cross section equal to the inelastic cross section or to use a mixture of MINBIAS and TWOJET events.

2.1.2 Twojet

All order s2 QCD processes, which give rise in lowest order to two high-pt jets. Included are, e.g.

g+g g+g g+q g+q g + g q + q?

Masses are neglected for c and lighter quarks but are taken into account for b and t quarks. The Q2 scale is taken to be

Q2 = 2stu/(s2 + t2 + u2)

The default parton distributions are those of the CTEQ Collaboration, fit CTEQ5L, using lowest order QCD evolution. A few older sets of parton distributions are included. There

5

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download